"We think that was a complete ruse, to get Dad there," Coos County District Attorney Paul Frasier said.
The bloodshed did not stop there.
The son then drove 50 miles to Bastendorff Beach near the city of Coos Bay, where in the early morning hours Tuesday he opened fire on multiple parked vehicles, killing David Jesse Hortman, 43, of Walker, Michigan, as he slept in his car. Hortman was touring the Oregon coast after representing an Indiana recreational vehicle accessories company at a trade show.
As a final act, Brimhall shot and killed himself.
Inside Brimhall's car, authorities found shotguns, rifles, pistols, some large firecrackers known as seal bombs, and the makings for an improvised explosive device.
Officials say they don't know what caused Zachary Brimhall to snap, or what he planned to do with the explosives. He left no suicide note.
"A lot of times in these cases, unless they left something in writing someplace or told somebody what they were planning on doing, it is really hard sometimes to find out the motivation for these things," Frasier said.
Not much is known about Zachary Brimhall. Frasier said he didn't have a job, and lived with his parents in Dillard, a small town about 80 miles inland from the killing scene on Bastendorff Beach. His father worked at a wood products mill in Dillard. Zachary Brimhall appears to have no criminal record.
Frasier said he knows of no signs of discord between Zachary Brimhall and his father. The weekend before the killings, Zachary Brimhall picnicked with his parents at a remote spot in the Coast Range and then stayed behind to camp while they returned home.
Early Tuesday morning, police responding to 911 calls of shots fired at Bastendorff Beach found Hortman dead in the driver's seat of his car, which had been hit by at least 15 shots fired from 100 yards away. One of the bullets hit Hortman in the side. They also found Zachary Brimhall dead of a self-inflicted gunshot wound in his car, an old AMC Pacer station wagon. Four other vehicles, three with people sleeping in them, were hit by 15 to 20 shots each, Frasier said. None of the people were hit.
Deputies went to inform Zachary Brimhall's family of his death, and to make sure he hadn't killed anyone at home, Frasier said.
There his mother told them that her son had called his father for help, saying his car wouldn't start, and the father had not come home. The last she saw of Zachary was at the weekend picnic.
When they got to the picnic spot, investigators found Ray Brimhall's white SUV. They waited for the bomb squad to check it out due to the explosives found in his son's car. They found Ray Brimhall's body nearby.
"He was shot multiple times, in excess of five times, probably in excess of 10," Frasier said.
David Hortman's family is trying to make sense of his death.
"He was just enjoying the view of the beach and the sunset," his niece, Sarah Hudson, told the Grand Rapids Press.
"We didn't expect anything like this to happen."
Hortman had told a co-worker at a recreation vehicle show in central Oregon that he was renting a car and taking a week off to drive the Oregon Coast, just looking at the ocean and sleeping in his car, Frasier said.
Hudson said her uncle was a technical writer for a recreational vehicle accessories manufacturer, working in Indiana during the week and returning to Michigan on weekends to care for his mother.
She said he was artistic, a "jokester" and a family-oriented man who loved to travel and appreciated the beauty of the shoreline, which may explain why he decided to sleep in his car.